DENVER -- Rockies left-hander Jorge De La Rosa's brown eyes burn with intensity. The scowl bubbles to the surface at times, like Wednesday night in the first inning when plate umpire Jeff Nelson called a ball on what De La Rosa thought was a good pitch to the Royals' Billy Butler. Often, the batter buys into the intensity and his mind begins to expect the 92-95 mph fastball De La Rosa is capable of throwing.

When he has the batter feeling his heat, and gearing for the heater, De La Rosa has the at-bat right where he wants it. Once known for throwing even harder, and having little control of the pitches and less of his emotions, De La Rosa has learned to use all the bluster to his advantage.

The ability to change speeds -- to grimace and whip his arm to the plate, only for the ball to arrive 10 mph slower to a wound-up batter -- has made De La Rosa the most successful pitcher in Coors Field history. Since joining the team in a trade with the Royals in 2009, De La Rosa has put himself in the conversation when it comes to the best pitchers in Rockies franchise history.

The mix of the top-end fastball, a cut fastball that has become a weapon against right-handed hitters and a changeup that has become his best pitch helped De La Rosa prevail Wednesday night, when he threw eight innings of a 5-2 victory over the Royals at Coors.

Forget those eyes. The changeup is the window to De La Rosa's pitching soul.

"Before, I would just throw the ball," De La Rosa said. "I didn't think about it. I would just try to break the catcher's glove. Right now, I know how to pitch, and I'm better.

"For me, it's one of the best pitches in baseball. It's really similar to the fastball. It has the same rotation and everything. When I learned to throw the changeup for a strike in any count, I became a much better pitcher."

De La Rosa snuck in a few curveballs and sliders, but the fastball-cutter-changeup mix was good enough to confound the Royals, who managed but two runs on five hits in the eight innings. De La Rosa tied a Rockies record by throwing the sixth game with four double-play grounders. His final impression was a changeup that fooled Christian Colon into ending the eighth with a double play.

Royals manager Ned Yost understands De La Rosa, because he knew him when.

Yost managed the Brewers when De La Rosa made his Major League debut Aug. 14, 2004, in a loss to the Marlins. De La Rosa had been with the D-backs twice, and in the Mexican League and with the Red Sox in between. With the Brewers 2004-06 and with the Royals in 2006 until he was traded to the Rockies for pitcher Ramon Ramirez on April 30, 2006, and even beyond, De La Rosa did not have the full package.

"He was 97 mph with his fastball and on days he was throwing it for strikes, he was unhittable," Yost said. "But, you know, that was like one out of four days. His fastball command was all over the map. He's harnessed that now. He's throwing more strikes with his fastball, his changeup is much improved and his curveball is more consistent."

De La Rosa began to change in 2009 and 2010 with the Rockies, when the club helped him find a better handle on his emotions and helped his changeup flourish. Wednesday's win was his 68th, four behind the club record held by Aaron Cook. De La Rosa's 44-14 home record has produced a.759 winning percentage that tops all pitchers with at least 25 starts at Coors. Only the Dodgers' Zack Greinke, who has pitched for the Royals, Brewers and Dodgers, has a higher winning percentage in his home parks (.770) among active pitchers.

Many pitchers have lived with hard sinkers, with Cook, Jason Jennings (58 wins) and Pedro Astacio (53 wins) among them. Ubaldo Jimenez, now with the Orioles, won 56 games with high velocity and a power sinker. But De La Rosa and Jeff Francis (64 wins) have shown you can win by trying softer.

"The changeup, that's his money-maker," Rockies manager Walt Weiss said. "It's a great pitch. He speeds hitters up with the cutter. That cutter-changeup mix has been really good. Once in a while, he'll pop a fastball in there at 95, maybe sneak a curveball in and get a strike early in an at-bat.

"The last couple years, even during tough times, when we've struggled and wins have been tough to come by, Jorge goes out there and wins games. He's got 13 wins now."

De La Rosa is a free agent at season's end, although the Rockies are expected to make a play for him. De La Rosa said Wednesday he doesn't want to talk about that; he wants to concentrate on confounding hitters.

"You can get a lot of hitters because they're looking for a fastball," De La Rosa said. "I learned the changeup when I was in Little League, and I watched how other pitchers played with hitters. It seemed I learned how to do it as soon as I got here."